Climate data were gathered from multiple sources (Assel, 2003, Hunter and Croley, 1993, International Great Lakes Datum, 1985 and Quinn and Norton, 1982) as well as from weather stations from the NOAA National Climatic Data Center (see Fig. 1 and S1) and Hunter and Croley (1993), which has been continuously updated online since the original publication date (http://www.glerl.noaa.gov/data/arc/hydro/mnth-hydro.html). Relationships between variables were analyzed with Pearson’s correlation and linear regression, all with alpha = 0.05 level. Land use, population, employment, income and households were used as indicators to represent direct and indirect drivers of change induced by human activities
and to better understand
the economic status of the human population. While we are aware of the selleck inhibitor differences between the political and watershed boundaries, our analysis of the socioeconomic system is based on the data obtained at the county level. We also obtained historical data from the Detroit metropolitan area on the USA side because it is a significant driver of change and provides a comparison to the other counties within the LSC watershed. Estimates of the area of the watershed and the land use characteristics check details were obtained from land use classifications produced by Agriculture and Agri-Food Canada (date of access 8 April 2012, ftp://ftp.agr.gc.ca/pub/outgoing/aesb-eos-gg/LCV_CA_AAFC_30M_2000_V12) and the US Multi-Resolution Land Characteristics Consortium (Fry et al., 2011). Because there were little land use data readily available in 1900, we used a USGS image (United States Geological Survey, access date 31 January 2013, http://www.epa.gov/med/grosseile_site/indicators/landuse.html) of why the Detroit metropolitan area to display snapshots of developed land use from 1905, 1938, 1968, and 2001. Socioeconomic data (human
population, households, water and waste water infrastructure, employment and income data) were gathered from USA sources: US Census Bureau (census data accessed 2 May 2012, http://www.census.gov/prod/www/abs/decennial/index.html), Southeast Michigan Council of Governments (SEMCOG, 2002), Camp Dresser and McKee (2003), CH2M HILL (2003), City of Detroit (1959), Detroit Water Service (1966), Morrill (1939), SEMCOG, 1971 and SEMCOG, 2001, St. Clair Regional Planning Commission, 1960 and St. Clair Regional Planning Commission, 1969, State of Michigan (1966), Tetra Tech MPS (2003), Michigan Department of Environmental Quality (access data 11 April 2012, http://www.deq.state.mi.us/owis/Page/main/Home.aspx), and Drinking Water Protection Network (access date 11 April 2012, www.rwqims.com) and from Canadian sources: Ontario Department of Economics and Development (1967), Statistics Canada (date of access, 10 July 2012, http://www12.statcan.gc.ca/census-recensement/2011/dp-pd/prof/index.cfm?Lang=E&TABID=1#tab1 and http://www.statcan.gc.ca/start-debut-eng.